Method of and apparatus for comparing information



May 25, 1954 C. HILLYER METHOD OF ANDAPPARATUS FOR COMPARING INFORMATION Filed March 25, 1952 4 She ets-Sheet 1 Fl G. I sYNcHRoNIzER I .E- //3 3 REFERENCE ANALYZING INDEPENDENT 4 SEARCHING DATA SOURCE cIRcuIT DATA souRcE cIRcuIT REFERENCE INDEPENDENT wAvE -l6 7-- WAVE TRANsDucER TRANSDUCER l8 AMPLITUDE DIFFERENCE 4 GENERATOR I EFFEcTIvE ANALYZING AMPL'TUDE PERIoD SIGNAL RESETTER GENERATOR 22-'IND|cAToR A 9 II /3 I2 I l I REFERENcE ANALYZING INDEPENDENT DATA souRcE CIRCUIT 1 DATA SOURCE l 6 A4 REFERENcE INDEPENDENT WAVE SYNCHRONIZER wAvE --/'7 TRANsDucER TRANSDUCER /8\ AMPLITUDE T DIFFERENCE 4 GENERATOR Y ANALYZM gggggg; 2 PERIOD REsETTER S'GNAL GENERATOR PREDETERMINED .E, MATCH FIG 5 22 UTILIZATION INVENTOR. APPARATUS CURTIS HILLYER CMQM HIS A ORNEYS.

y 25, 1954 I c. HILLYER 2,679,636

r METHOD OF AND APPARATUS FOR COMPARING INFORMATION Filed March 25, 1952 4 Sheets-Sheet 2 HORIZONTAL HORIZONTAL ANALYZING SEARCHING MIXER SWEEP SWEEP VERTICAL VERTICAL ANALYZING SEARCHING MIXER SWEEP SWEEP 54 35 I I 47 49 55 3 32 SYNCHRON'ZER --42 --33 AMPLIFIER SUBTRACTOR AMPLIFIER FULL WAVE. 2 RECTIFIER I I INVENTOR.

CURTIS HILLYER BY WIB HIS A ORNEYS.

May 25, 1954 C. HILLYER METHOD OF AND APPARATUS FOR COMPARING INFORMATION Filed March 25, 1952 SYNCHRONIZER 4 Sheets-Sheet 3 SEARCHING CIRCUIT 4 /2 i REFERENQE 4 ANALYZING INDEPENDENT DATA SOURCE c T DATA SOURCE REFERENCE INDEPENDENT WAVE -/6 /7- wAvE TRANSDUCER TRANSDUCER I8 I AMPLITUDE DIFFERENCE GENERATOR ANALYZ'NG ELFPELCIILVDEE PERIOD SIGNAL RESETTER GENERATOR I I "I 2! LEAST sEARcI-IINc 7 SIGNAL PERIOD STORER RESETTER IMPROVEMENT sENsER SEARCH SEARCHING 73-" PORTION PERIOD IDENTIFIER REsETTER UTILIZATION APPARATUS NvEN-roR.

CURT IS H ILLYER H IS ATTORNEYS.

May 25, 1954 C. HILLYER METHOD OF AND-APPARATUS FOR COMPARING INFORMATION Filed March 25, '1952 4 Sheets-Sheet 4' HORIZONTAL HORIZONTAL ANALYZING SEARCHING HOR'ZONTAL SWEEP SWEEP M'XER VERTICAL VERTICAL 47 VERTICAL ANALYZING SEARCHING SWEEP SWEEP M'XER I i I 35 I I 49 55 3 32 SVNCHRON'ZER 33 42 45 56 57 AMPLIFIER SUBTRACTOR AMPLIFIER FULL WAVE RECTIFIER V 82 PHASE INVERTER E DISCHARGE DISCHARGE .T|ME DELAY H CIRCUJT v III\ PHASE INVERTER DIFFERENTIATOR DISCHARGE CIRCUIT TIME D-ELAY 98 i I06 99 I I .L

F I P I I0! DISCHARGE L IIQW I07 CIRCUIT a I I 2 m #755 I INVENTOR. PEAK PEAK CURTIS HILLYER VOLTMETER VOLTMETER BY I HIS ATTORNEYS- Patented May 25, 1 954 UNITED STATES PATENT OFFICE 2,679,636 METHOD or AND APPARATUS FOR COMPARING INFORMATION Curtis Hillyer, Short Hills, N.- J. Application March 25, 1952', Serialllo. 273,517

9 Claims. 1

The present invention relates broadly to the comparison of information by operating upon waves that embody such information;

More specifically, the invention contemplates determining the degrees of similarity between parts of a large mass of arbitrarily complicated information and a particular piece of information which may be a part of another mass of complex information. The large mass of information may be derived from an independent data source and compared with a particular piece of information from a reference data source under local control. On the other hand, the independent data source may supply a particular piece of information which is matched with parts of a large mass of recorded reference information.

The degrees of similarity between the particular piece of information and the parts of the mass of information may be indicated as a function of the locations of the parts in the mass. Alternatively, an indication may be produced whenever a match of predetermined quality is encountered. In still another form of the invention, all parts of the mass of information are investigated and then the location of the part that most closely approximates the particular piece of information is identified. V

In order to identify unambiguously a very small part in a mass of information, the present invention makes use of some of the original context, that is, the environment of the part, on the theory that a very small part is only unique in its relationship to other contiguous or closely associated parts. For example,- a reference point on a monochrome photograph cannot be unambiguously located on' a second monochrome photograph Without taking. into account the:

character of the points closely adjacent the reference point, since the reference point is characterized only by a particular tone andthere will usually be many points having substantially identical tones.

The amount of' context which must be considered depends upon the character of the information. Correct identification of'a particular very small part in a mass of regular or monotonous information requires a substantial amount of context. Thus, a specific point a. repeti tivepattern cannot. be located Without examining a rather extensive area surrounding'the point.

In accordance with the present invention; the mass of information, wherein the particular piece of information is to' be located; is represented by a first series of Waves" which are not 6 and series of waves are generated in synchronism.

If the independent data source is not subject to local timingcontrol, the independent data waves must serve as a timing standard. Each inde pendent data wave is opposed to its associated reference data wave, for the purpose of deriving a third series of Waves representing the instantaneous amplitude differences between the op posed waves. 7 y

The effective amplitude of each wave representing the instantaneous amplitude difierences between each pair of simultaneously generated reference and independent data waves is indicat-ive'of the" degree ofmatch between such waves. In other words, the area defined by the instantaneous amplitude differences during eachone of the third series of waves is a measure of the match between those portions of the referenceand independent data being investigated. 'It is to be understood that-positive areasin the wave are to be added to rather thansubtracted from negative areas unlike" an averaging process. The effective amplitude may be measured by some type of integrating operation.

Each signal indicative of the degree of match may be displayed as a function of the number of the attempt to obtain a match or as a function of the time positionof such attempt. Alter-- nativel y, the signals indicative of the degree of match may be operated upon to detect a predetermined quality of match or to select the optimum match from among a series of' attempted matches;

In order that the invention maybe morefully understood, it will now be" described in detail" with reference to the accompanying drawings wherein:

Figure 1 is a block diagram illustrating a form of the" invention indicating the existence of a match of predetermined quality with reference to the position of the match or the degree of each match with reference to the-position of such match;

Figure 2 is a block diagram of a particular embodiment of the form of the invention illustrated in Figure 1;

Figure a block diagram illustrating a form of the invention indicating the position of optimum match;

Figure 4 is a block diagram of a particular embodiment of the form of the invention illustrated in Figure 3; and

Figure is a block diagram illustrating a form of the invention indicating the occurrence of a match of predetermined quality.

Similar reference numerals are used in the drawings to 'indicate corresponding parts.

Referring now to Figure 1, a reference data source .H contains information which at least approximately corresponds to some information mixed with a much larger mass of information contained in an independent data'source 12'. The substantially constant reference. information is converted into a first series, of recurrent a particular form of the system discussed with reference waves by means of an'analyzing circuit l3 timed by a synchronizer'l l. The analyzing circuit I3 also converts a selected portion of the .data in the source ,12v -into a second series of independent waves. The portion of independent data that'is thus converted is" selected by a searching circuit [5 which is also timed by the synchronizer l4. The action of the searching circuit I5 is much slower than the analyzing circuit l3 and serves to change gradually or'in a third series of waves having instantaneous amplitudes corresponding to the differences between the amplitudes of the applied waves.

The difference waves are supplied to an effective amplitude signal generator [9 which integrates the positive and/0r negative portions of the waves without regard to polarity to obtain successiveintegral signals having amplitudes indicative of the degree of match between the reference and independent waves. At the end of each analyzing period, a resetter 2I restores the generator I9 to a reference condition, and the integral signal is supplied to an indicator 22. The indicator 22 is also under the control of the searching circuit [5 and 'is adapted to display the degree of match with reference to the time .or space position of the portion of. the data in quality withreference to the position of ;the-

match.

The data that is compared maybe derived from any one of various possible sources. example, the independent sourcel2 may comprise a landscape or Seascape which is analyzed by means of the analyzing circuit [3 in the form of a pulsed radar system. Under these circumstances, the search circuit l5 may comprise 'mea'nsfor varying the direction of the radar beam to alter the portion of the terrain being analyzed. The reference data source H may be a storagetube.

The transducers l6 and I! generally include amplifiers having substantially similar characteristics. The upper and lower limits of the necessary frequency response are determined in part by the fineness andcoarseness, respectively,

For

tube 43.

"reference to Figure 1. -2 serves to locate data contained on a sheet 3| and corresponds to the reference data.

of the detail in the information. Increased accuracy of match or speed of match both raise the required upper limit of frequency response.

The indicator 22 may comprise a cathode ray tube providing a two-dimensional display of degree of match versus time or position of match.

Alternatively, it may include a gated mixer tube which passes a signal having an amplitude proportional to the time or position @of match only inresponse'to a signal fr-omth'e effective amplitude signal generator. l9 having an amplitude indicative of a predetermined quality of match,

for example, a substantially perfect match.

Known types of counting circuits may likewise be employed in the indicator 22.

' Referring now to Figure 2, there is illustrated The apparatus of Figure among a much larger mass of data contained on a sheet 32. It is immaterial-which sheet represents reference data. The data is represented as variations in tone over a surface and may take such forms as adrawing, a printed or written page, or a photographic reproduction.

Sheets 3| and 32 are shown, for example, to be positive or negative photographic transparencies.

supplies synchronizing A synchronizer 33 pulses to a horizontal analyzing sweep circuit 34 and a vertical analyzingsweep circuit 35. The output circuits of the horizontal and vertical analyzing sweep circuits 34 and 35 are connected to corresponding cathode ray deflection of the face 39 of the tube 38 focuses the luminous Beneathspot upon the surface of the sheet 3|. the sheet 31 is a second. lens system 42 which collimates the light transmitted from the area covered by the flying spot on the sheet 3| and directs a beam of light onto a photosensitive The photosensitive tube 43 is adapted to generate a voltage proportional to the instantaneous intensity of the received light beam The voltage thus generated varies in accordance with photographic densities encountered by the luminous spot as it is swept over the sheet 3| A voltage amplifier 44 amplifies the signalgenerated by the photosensitive tube 43 and applies the same to a voltage subtractorcircuit 45.

The synchronizer 33 likewise supplies triggering pulses to horizontal and vertical searching sweep circuits 46and 41. The output circuits of the sweep circuits 46 and "4'? are connected to voltage mixers and 49, respectively, whereinthe searching sweep voltages are combined with the analyzing sweep voltages from the sweep circuits 34 and 35, respectively. The output circuits of the horizontal and vertical mixers 48 and 49.

are connected to a pair of deflection circuits 5! area swept out by means of the cathode ray'tube 38 on the sheet 31. At the sametime, however, the searching sweep acts to move the analyzing rea s. a esu a msn a eve t e su f 1 h? sheet 32, soas to describe a search-ing area which may be relatively large comparison to the analyzing area. 1

Beneath the sheet 32" afurth-er lens system 56 gathers the light transmitted through the sheet 32 and directs it upon a photosensitive tube 57. The photosensitive tube 51 generates a voltage dependent upon the photographic densities encountered by the luminous spot as: it travels over the surface of the sheet 32'. The voltage generated by the photosensitive tube 51 corresponds to the independent data, and after amplification inan amplifier 58 having a gain control 59, is applied to the subtractor circuit 45.

The subtractor circuit 45 mutually opposes the instantaneous amplitudes of the two signals supplied from the amplifiers M and 58 and applies the resultant signal to a full-wave rectifier 6!. The rectifier 6| converts: the signal from the subtractor circuit 45 into a direct voltage having an amplitude corespond-ing to theabsolute instantaneous amplitude difference between the signals coming from the amplifiers 44 and 58. This fluctuating direct voltage is applied to the control grid 62 of a cathode ray tube Git-having horizontal and vertical deflection coils 64 and 85 connected to the horizontal and vertical searching sweep circuits 4B and 41-, respectively.

Inasmuch as the intensity of the cathode ray beam is under the control of a unidirectional voltage representing the instantaneous amplitude differences, the relatively long persistent fluorescent material on the face 66 of the tube 63 tendsto generate a luminous spot which has a light intensity indicative of the degree of match between the reference data and the independent data. The deflection coils 6'4 and 65 simultaneously position the luminous spot with reference to the location of the analyzing area on the data sheet 32. Accordingly, the face 66 of the cathode ray tube 53 displays in two dimensions the degree of match between the lesser data and each portion of the greater data. The best or the worst match can be readily determined.

If the lesser data. is changing slowly relative to the searching period, it isevident that the optimum match may be monitored, and, if desired, the position of the sheet 32 may be moved to maintain a substantially constant apparent location of the lesser data.

There is of coursea widevariety of information which may be represented on sheets 3! and 32. These sheets may, for example, comprise stereoscopic pairs of photographs. If these photographs have been rectified, that is, corrected for tilt and tip by rephotographing the original photographs at appropriate angles, the cathode ray tube 66 will indicate a substantial match at a location corresponding to the stereoscopic displacement of the picture element being analyzed. The sheets 3 l. and 32v may be synchronously manually or mechanically moved to analyze contiguous picture elements. The tube 66 will then indicate a series, of stereoscopic displacements which, when suitably corrected, are measures of the elevations of the corresponding portions of the photographed terrain.

The analyzing-and searching circuits may take many forms and the use of horizontal, and vertical sweeps in cathode ray scanning tubesis illustrative' only. Specifically, image scanning tubes may beused in. place of the. photosensitive tubes 3 and 51. with an extended source of illumination replacingv the cathode ray tubes 38 and 53; Differ-- i capacitor 84 has an increasing value with a deand the deflection coils 36 31 and 5 52' would be modified for use with 'theimage scanning tubes.

It is preferable to. provide amplitude controls as well as position controls for all the sweep circuits in order to adjust the size: or shape of the analyzing or searching patterns to suit the detail on the sheets 31 and 32.. For example, pictures having very fine detail require. a smaller analyzing pattern to respond to the fine variations and to avoid ambiguities caused. by repetitive detail as compared to pictures having coarse detail which can be scanned more rapidly and witha larger analyzing pattern. The searching. pattern should be large enough. to more than. cover areas which may have no detail in order to maintain a continuous basis for comparison. However, a very large pattern will include a needlessly wide variety of non-related data and. tax the capacity of the apparatus. v

The first portion of the structure of Figure 3 is similar to the system shown in Figure 1 and similar reference numerals indicate corresponding parts. The indicator 22 is, however, replaced by a group of. circuits which identify the position of best match after the conclusion of a predetermined number of attempts to obtain a match.

At the end of each analyzing period. when the resetter 2| restores the. generator H! to a reference condition, the effective amplitude signal is transferred to a least amplitude storer' 111.. The storer II is receptive tov the efiectivIe; amplitude signal applied to it only if the amplitude of the signal is indicative of a. better match: than the match indicated by a prior stored signal.

Whenever the storer H accepts a. signal, a pulse is generated by a match improvement sensor 12 and applied to a search portion identifier 13. The pulse causes the identifier 13. to generate, and store an identification signal corresponding to the signal momentarily being produced: by the searching circuit 15. At the end of the search period, the resetters 14 and lireturn the least amplitude storer H and the search portion identifier 13, respectively, to their reference conditions. At this time, the final identification signalfstored by identifier 13 is applied to utilization apparatus 8! is shown as a multi-grid electron tube 82 hav-.

ing a cathode 83 normally isolated from ground by a capacitor 8'4 The charge on the" capacitor 3i is placed at a convenient reference value, for example, zero, at the commencement of each analyzing period bya discharge circuit 85 under the control of the synchronizer 33. The signals from rectifier B l are applied: with. negative polarity to the controlgrid 86 of the tube 82. The normal conduction current through the tube 82' acts to charge the capacitor 84'- to amaximum value in the absence of any appreciable applied signal during the analyzing period. In the presence of any signal from the rectifier 6f, the current flowing into thecapacitor84-isreduced. The charge and, consequently, the voltage across the 7 creasing effective amplitude difference between waves issuing from the amplifiers .44 and 50.

Accordingly, the amplitude of the voltage generated by the integrator 8| and appearing across capacitor 04 is indicative of the degree of match between the data. beinganalyzed on the sheet 3| and the datacomprising a portion of the sheet 32.

The output voltage from the integrator 8| representing the degreeof match is applied to a gate circuit 81. In order that the gate circuit 8'! respond only to the finalamplitude of the signal derived from the integrator 8 I ,a control pulse is applied from the synchronizer 33 over a lead 88. This control pulse renders the gate circuit 81 sensitive to the output of the integrator 89. A time delay circuit 89 is interposed between the discharge circuit. 85. and the synchronizer 33 in order that the full voltage across the capacitor 84 in the integrator 8| be applied to the gate circuit 81 before the capacitor 84 is discharged and placed in condition for determining the area defined by the instantaneous amplitude differences during the next analyzing period. The gate circuit 81 comprises a multi-grid electron tube 9| having its cathode 92 isolated from ground by a capacitor 93. This capacitor biases the tube in accordance with the stored charge. Accordingly, no additional charge is stored unless the voltage applied to the control grid 94 of the tube 9| is greater than that already on the capacitor 93.

A diiferentiator95 is connected to the capacitor 93 in the gate circuit 81 and is responsive to any increase in the stored voltage. In other words, it produces a pulse in response to any improvement in the match.

The pulses generated by the diiferentiator 95 and signifying the best match so far are applied lar gated mixer circuits 91 and 9B. Circuits 91 and 98 comprise multi-grid electron tubes 99 and IN, respectively, having cathodes I02 and I03, respectively, isolated from ground by capacitors I04 and I05, respectively. The second control grids I06 and I! in the tubes 99 and |0I are supplied voltages over leads I08 and M9, respectively, connected to horizontal and vertical searching sweep circuits 4% and 41, respectively, and representing the horizontal and vertical locations of the analyzing sweep on the sheet 32.

Whenever a gating pulse is received from the differentiator 95, voltages are transferred to the cathode storage capacitors I04 and I which are proportional to the vertical and horizontal positions of the portion of the sheet 32 that has just been analyzed. The storage capacitors I04 and I 05 are discharged before the application of each pulse from the diiferentiator 95 by the delaying action of the time delay circuit 96 which permits the synchronizer 33 at the end of each analyzing period and applies the same in the form of negative blanking pulses to a second grid 80 of the tube 82 in the integrator circuit 8|. rangement prevents the integrator 8| from operating on spurious signals which may occur This arthrough a time delay circuit 96 to a pair of simiduring the return of the vertical analyzing sweep between the end of one analyzing period and the beginning of the next. p,

A discharge circuit I I1 is coupled to the storage capacitor 93 in the output of the gate circuit 81 to discharge the same'at the end of each search portion of the sheet'32 thatbest matches the.

analyzed portion of the sheet 3|.

Referring now to Figure 5, a particular piece of information or reference data, whichis recorded in the reference data source II, may be detected among a mass of information derived from an independent data source I2 in the form of a sequence of independent waves. The independent data source |2', may, for example, comprise a train of sound or lightwaves whereas the reference data may be recorded on a magnetic tape or an image. storage tube. The reference data is recurrently converted into a reference wave in synchronism with significant portions of the waves from the indepedent data source I2. This is accomplished by means of the analyzing circuit I3 acting under the control of a synchronizer' I4 which is in turn timed by characteristic portions, for example, by the abruptly rising intensity, of the electrical waves generated by the independent Wave transducer II, which waves correspond to the waves from the independent data source I2. The reference wave transducer I6 converts the data analyzed by the analyzing circuit I3 into electrical reference waves each of which is applied to the ainplitude difference generator IS in opposition to the associated independent wave from the transducer H.

The amplitude difference generator I8 is connected to the effective amplitu de signal generatorto the output of the efiective'amplitude signal generator I9 and is adaptedto generate a si nal whenever the amplitude of the applied effective amplitude signal indicates that the match between the reference and independent waves has reached some desired value. When this occurs the senser I2I supplies a signal to a utilization apparatus I22. Theutilization apparatus I22 may, for example, comprise an alarm or control circuit or may otherwise indicate the occurrence of the anticipated condition.

A suitable application of the arrangement of Figure 5 would be where only knowledge of the existence of the reference data among the independent data is desired or where the reference data is capable of being located in time but not in space. I t t The presentinvention is capable of comparing any information which can be expressed in terms of waves. For example, if a single frame of motion picture film is employedas the source of in-' dependent data, a. vast, number. of -reference.

9 frames may be searched until a substantial matching of wave shapes indicates that the 'corresponding reference picture frame has been found. The searching cycle may thereupon be terminated.

It is not necessary that the reference information be substantially constant, although this is true in the usual case. An exception occurs when both reference and independent data are changing and it is desired to detect a fortuitous match of predetermined quality.

In view of the many forms that the invention may assume, the illustrated embodiments are not to be regarded as limiting the appended claims.

I claim:

1. Apparatus for determining the degree of match between a first series of waves of general- 1y varying shape and a second series of waves of generally constant shape comprising means for subtracting the instantaneous amplitudes of each wave of one of said first and second series from the instantaneous amplitudes of each concurrent wave of the other of said first and second series to obtain a third series of waves, and means for integrating the instantaneous amplitudes throughout each of said third series of waves to determine the degree of match.

2. Apparatus for determining the best match between a first series of Waves of substantially constant shape and a second series of waves of generally varying shape comprising means for subtracting the waves of the first and second series from each other to obtain a unidirectional third series of waves, means for integrating the waves of the third series to obtain an integral signal indicative of the degree of match between the first and second series of waves, means for storing the integral signal whenever the degree of match is improved, means responsive to improvement in the match for storing an identification signal that identifies which wave of the second series was being matched, and means for transmitting the final stored identification signal after the end of the second series of waves to effect said determination.

3. Apparatus for determining which wave of a series of waves has the greatest amplitude comprising means for generating a timing signal for identifying each wave of said series, means for storing a signal having an amplitude dependent upon the amplitude of a wave whenever said wave is greater than any prior wave, means responsive to increase in the stored signal for storing an identification signal having an amplitude dependent upon the amplitude of the timing signal, and means for supplying the final stored identifiaction signal after the termination of said series of Waves to effect said determination.

4. Apparatus for indicating the degrees of match between a particular piece of recorded information and a mass of recorded information comprising means for analyzing a selected portion of the mass of information to generate a first series of waves, means for simultaneously analyzing the particular piece of information to generate a second series of waves, means for altering the selection of the portion of information to investigate said mass of information, means for opposing each wave of said first series with the simultaneously generated wave of said second series and for rectifying the resultant wave to obtain a series of unidirectional waves representative of instantaneous amplitude differences, and means for integrating the instantaneous amplitudes throughout each unidirectional wave to pro- 10 duce signals having amplitudes indicative of the degrees of match between-simultaneous waves of said first and second series.

5. Apparatus for indicating a predetermined degree of match between a particular piece of recordedinformation and a mass of recorded information comprising-means for analyzing a selected portion of the mass of information to generate a first series of waves, means for simultaneously analyzing the particular piece of information to generate a second series of waves, means for altering the selection of the portion of information to investigate said mass of information, means for opposing each wave of said first series with the simultaneously generated wave of said second series and for rectifying the resultant wave to obtain a series of unidirectional waves representative of instantaneous amplitude differences, means for integrating the instantaneous amplitudes throughout each unidirectional wave to produce signals having amplitudes indicative of the degrees of match between simultaneous waves of said first and second series and means for generating a further signal identifying the variable portion of the mass of information that was being analyzed when the-degree of match reached a predetermined value.

6. Apparatus for indicating the degrees of match between a particular piece of recorded in formation and a mass of recorded information comprising means for analyzing a selected portion of the mass of information to generate a first series of waves, means for simultaneously analyzing the particular piece of information to generate a second series of waves, means for altering the selection of the portion of information to investigate said mass of information, means for opposing each wave of said first series with the simultaneously generated wave of said second series and for rectifying the resultant wave to obtain a series of unidirectional waves representative of instantaneous amplitude differences, means for integrating the instantaneous amplitudes throughout each unidirectional wave to produce signals having amplitudes indicative of the degrees of match between simultaneous waves of said first and second series and means for indicating said signals with reference to the location of the portion of the mass of information that is being analyzed.

7. Apparatus for indicating the optimum degree of match between a particular piece of recorded information and a mass of recorded information comprising means for analyzing a selected portion of the mass of information to generate a first series of waves, means for simultaneously analyzing the particular piece of information to generate a second series of waves, means for altering the selection of the portion of information to investigate said mass of information, means for opposing each wave of said first series with the simultaneously generated Wave of said second series and for rectifying the resultant wave to obtain a series of unidirectional waves representative of instantaneous amplitude differences, means for integrating the instantaneous amplitudes throughout each unidirectional wave to produce signals having amplitudes indicative of the degrees of match between simultaneous waves of said first and second series and means for generating a further signal after the mass of information has been investigated identifying the variable portion of the mass of information that was being analyzed when the degree of match reached an optimum value.

8. Apparatus for determining the degrees of match between a first series of waves of generally varying shape and a second series of waves of generally constant shape comprising means for opposing each wave of said first series and a simultaneously generated wave of said second series to obtain a third series of waves representative of instantaneous amplitude differences, and means for integrating the instantaneous amplitudes throughout each wave of said third series to produce signals having amplitudes indicative of the degrees of match between simultaneous waves of said first and second series.

9. Apparatus for determining a predetermined degree of match between a first series of waves of generally varying shape and a second series of waves of generally constant shape comprising means for opposing each wave of said first series and a simultaneously generated wave of said second series, means for rectifying the resultant waves to obtain'a'series of unidirectionalwaves representative of instantaneous amplitude differences, means for integrating the instantaneous amplitudes throughout each unidirectional wave to produce signals having amplitudes indicative of the degrees of match between simultaneous waves of said first and second series, and means for generating a signal whenever the degree of match exceeds a predetermined value.

References Cited-in the file of this patent UNITED "STATES PATENTS 

